The present invention relates generally to the field of magnetic data ea storage and retrieval. In particular, the present invention relates to high magnetic moment seed layer materials for use in forming a writer pole tip.
A typical magnetic recording head consists of two portions: a writer portion for storing magnetically-encoded information on a magnetic disc and a reader portion for retrieving that magnetically-encoded information from the disc. The reader typically consists of two shields and a magnetoresistive (MR) sensor positioned between the shields. Magnetic flux from the surface of the disc causes rotation of the magnetization vector of a sensing layer of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor. This change in resistivity of the MR sensor can be detected by passing a current through the MR sensor and measuring a voltage across the MR sensor. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary.
The writer typically consists of two magnetic poles separated from each other at an air bearing surface of the write head by a write gap and connected to each other at a region away from the air bearing surface by a back via. Positioned between the two poles are one or more layers of conductive coils encapsulated by insulating layers. The writer and the reader are often arranged in a merged configuration in which a shared pole serves as both a shield in the reader and a magnetic pole in the writer To write data to the magnetic media, a time-varying electrical current, or write current, is caused to flow through the conductive coils. The write current produces a time-varying magnetic field in the magnetic poles. The magnetic field bridges the write gap forming a write gap field. The magnetic media is passed over the air bearing surface of the writer at a predetermined distance such that the magnetic surface of the media passes through the gap field. As the write current changes, the write gap field changes in intensity and direction.
Recent years have seen a considerable increase in data storage densities. Generally, the data storage capacity of a magnetic data storage and retrieval device is increased through use of a magnetic media having an increased areal density, which is the number of units of data stored in a unit area of the media. Areal density is determined by two components of the magnetic media: the track density (the number of data tracks per unit width of the magnetic media) and the linear density (the number of units of data stored per unit length of a data track). To increase the areal density of a magnetic media, one must increase the linear density and/or the track density of the magnetic media.
Increases in areal density have been achieved by increasing the strength of the write gap field, decreasing the thickness of the gap between the magnetic poles at the air bearing surface, decreasing the width of the writer poles at the air bearing surface and increasing the coercivity of the magnetic media. These improvements require the material of the magnetic poles to conduct relatively high flux densities, especially those portions of the poles, i.e., the pole tips, which are adjacent to the gap. However, materials have a saturation level beyond which they will conduct no more flux. Accordingly, there is a need for a pole tip materials which have high saturation moments.
A magnetic recording head has a magnetic pole tip and a seed layer upon which the magnetic pole tip is formed. The seed layer is preferably formed of a high magnetic moment material having a saturation magnetization of at least 1.8 Tesla and a high resistance to corrosion. In preferred embodiments of the present invention, the seed layer is preferably formed of 2.1 Tesla Fe44-46Co39-41Ni14.5-15, 1.8 Tesla Fe54-56Ni27-29Co16-18 Tesla Fe86-90Cr10-14, or 1.9 Tesla Fe52-62Co26-36Cr10-14, wherein the subscripts indicate a preferred range of atomic percentages for each element in the given alloy.